Fuel flowing through a fuel injector typically exits at a nozzle end of the fuel injector. The nozzle end is believed to have a disk with at least one orifice to, in part, control the spray pattern and the direction of the fuel exiting the fuel injector.
The orifice is believed to be formed by drilling through a flat workpiece. The method of drilling orifices for fuel injector is believed to be electric discharge machining (EDM) that can form orifices of 150 to 200 microns in diameter. It is believed that one of the many disadvantages of EDM is the fact that the holes are typically formed without any favorable entry or exit geometry for the orifices, thereby affecting the flow through the orifices. It is further believed that EDM drilling for orifices smaller than 150 microns takes twice as long to complete. Moreover, it is believed that to maintain the same amount of fuel flow with the smaller orifice may require more than four times the number of the larger orifices. This is believed to reduce productivity in the manufacturing of the fuel injector. Additionally, it is believed that EDM forming of the orifices are not uniform between individual injectors, thereby causing the fuel injector spray to also be non-uniform between individual injectors.
Future emission standards for gasoline and diesel engines are believed to require the use of smaller orifices for smaller fuel spray droplets and shorter fuel spray duration. It is believed that fuel spray pattern and flow should remain uniform between adjacent cylinders in a multi-cylinder engine.
It is believed that smaller orifices can be formed with no loss in productivity through the use of lasers. At least two laser techniques are believed to be used for laser machining orifices. One is trepanning or helical drilling, the other is percussion drilling. Percussion drilling is believed to be less than desirable due to the random nature of metal heating and expulsion that most likely results in a non-cylindrical or non-circular orifice. Trepanning, on the other hand, is believed to be more precise as a center hole is believed to be initially formed before the formation of the orifice. Helical drilling is similar to trepanning but without the initial formation of a center hole. However, it is believed that neither trepanning nor percussion drilling provides for a desired formation of entry and exit geometry in the orifices.
The present invention provides for at least one method of forming chamfers and an orifice together while maintaining dimensional consistency between a plurality of orifices formed by the method. In one preferred embodiment of the invention, the method is achieved by providing a laser light source, extracting non-collimated light from the laser light source; extracting collimated light from the laser light source; forming at least one orifice in a workpiece with the collimated light directed at the workpiece at a predetermined first time interval; and forming at least one chamfer with the non-collimated at a second time interval simultaneous with the first time interval. The orifice formed by the method has an axis, which extends between a first surface and second surface of the workpiece, and the chamfers are disposed between the first surface and the second surface.
The present invention further provides an apparatus to form at least orifice and at least one chamfer in a workpiece together while maintaining dimensional consistency between a plurality of orifices. In a preferred embodiment, the apparatus includes at least a source of collimated and non-collimated light, a collimated light filtering assembly, a non-collimated light filtering assembly, and at least one shutter and at least one iris arrangements that direct collimated and non-collimated light at the workpiece to form the at least one chamfer and the at least one orifice which has an axis extending between a first surface and a second surface of the workpiece. The apparatus is configured such that at least one of the orifice and chamfer has a surface roughness of between approximately 0.05 microns and approximately 0.13 microns and a coefficient ratio of between approximately 0.6 and approximately 1.0.